The overall objective is an increased understanding of the molecular spectrum of mutations induced by nitroarenes in mammalian cells. The nitroarenes are widespread environmental pollutants that may prove to be harmful to man. We have previously shown that 2,4,7-trinitro-9- fluorenone (TNF) is more genotoxic than 1-nitropyrene. in four different mammalian cell lines. Moreover TNF exhibits clastogenic effects since it induces chromosome aberrations in both human lymphocytes and chinese hamster ovary (CHO) cells. Several studies in mammalian cells indicate that the mutational spectrum may include gross chromosomal lesions as well as single base point alterations. Clastogenic or radiomimetic agents, in particular, may yield more chromosomal lesions than point mutations. 1) We will use two CHO cell lines, namely the CHO-K1BH4 which contains a single copy line derived from the CHO-K1-BH4 cell, carries a stable deletion mutation of the HGPRT gene and contains a single copy of the xanthine-guanine phosphoribosyl transferase (gpt) gene integrated into an autosomomal site in the host genome. While both cell lines show equal cytotoxic responses to a variety of physical and chemical mutagens they show significantly different mutational frequencies to clastogens or radio-mimetic agents. 2) We will employ a rapid screening method using the polymerase chain reaction (PCR) to detect deletion mutations in the HGPRT and the gpt genes respectively. Deletion mutations occurring in exon 3 and exon 9 of the HGPRTgene will be screened by using pairs of oligonucleotide primer sets designed to amplify 276 and 344 base pairs of these two respective exons. Another set of primers are designed to screen 500 base pairs of the gpt gene. Additional primer sets and sequencing of the PCR products will be designed to refine the basic hypothesis and to screen for mutations that may occur in other regions of the gene and to search for putative hot spots of mutations in the HGPRT and gpt gene. The data obtained in this study will provide more information on the mutational spectrum induced in mammalian genes by nitroarenes.